The use of solid state ionic conductors allows for nano-scale patterning and stamping by highly localized electrochemical etching and deposition. When an electric field is applied by two electrodes in contact with a material that exhibits ionic conduction, the metal ions near one of the electrodes migrate through the bulk of the ionic conductor, and, upon receiving electrons at the counter electrode, reduce back to metal atoms precipitating at the interface. Alternatively, under a reverse potential, a counter electrode of the metal is etched. By nano-patterning the contact between the electrode and the ionic conductor, one can deposit or etch metal patterns at a conductive substrate.
Electrochemical micromachining, which works by local dissolution of a conducting substrate (metals, semiconductors) under an applied anodic bias in solution, shows promise in fabricating 3D micro and nanoscale structures and devices, since it requires relatively simple equipment and offers rapid etching compared to other techniques such as ion beam milling and laser abrasion. However, a liquid electrolyte, which is difficult to handle, is required as a conducting medium between the two electrodes. This challenge is overcome in the present invention by utilizing solid state ionic conductors.
Terabe et al, demonstrate the use of mass transport in ionic conductors to implement a quantized atomic conductance switch, QCAS, where the concept of formation and dissolution of nanometer silver cluster was used. In their QCAS, a silver wire with a thin layer of silver sulfide cover was laid on a substrate, and a platinum wire went across it with a gap of one nanometer [K. Terabe, et al., Quantized conductance atomic switch, Nature, Vol 433, 6, January 2005.]. By forming silver cluster from silver ions drawn from underlying silver wire and hence bridging the gap in between, the switch operated at room temperature at a frequency of 1 MHz.
Terabe et al, show formation and disappearance of nano scale metal cluster on the apex of an Scanning Tunneling Microscopy (STM) tip. Based on the concept of electrochemical reaction, they show growth and shrinkage of a silver pillar of 70 nm in diameter and 200 nm in length on a silver sulfide coated silver STM probe [K. Terabe, et al., Formation and disappearance of a nanoscale silver cluster realized by solid electrochemical reaction, Journal of applied physics, Vol 91, 12, June, 2002]. By controlling the current going tunneling through the STM tip and their sample, the growth rate of the silver cluster is regulated.
M. Lee et al. have used Atomic Force Microscopy (AFM), and a super ionic conductor material, RbAg4I5, for nanopatterning [M. Lee, et al., Electrochemical nanopatterning of Ag on solid-state ionic conductor RbAg4I5 using atomic force microscopy, Applied physics letters, Vol 85, 16, October 2004]. With pulsed electric field input through a metal coated AFM probe controlled to step across an RbAg4I5 sample, they were able to place nanoscale silver cluster with each pulsed bias input, and hence arrange the clusters in designed pattern.
The use of solid state ionic conduction for switches and for single-point direct writing (with a modified stylus tip) has been previously demonstrated.
None of those methods, however, are fully adaptable to massive manufacturing due to the slow serial scanning process. Accordingly, there is currently a need in the art for methods of manufacturing structures, including nanostructures, that are capable of high-throughput large area patterning. The invention disclosed herein is a stamping process that can simultaneously produce a number of spatial features and can scale-up to high production rates for massive manufacturing over a large pattern area that conventional approaches cannot match. An additional advantage of the present methods and systems is the ionic stamp can be programmed, scaled and reprogrammed with different metallic nanopatterns for processes such as nano imprint lithography, molding, transfer printing, etc. With appropriate solid electrolytes, the processes disclosed herein can be used to directly produce a structure or desired pattern of structures in different metallic films, substrates, bulk materials or surfaces, thereby saving steps compared to a conventional photolithography patterning process. The patterning systems and methods of the present invention are particularly suited for manufacture of patterns for use in devices having high sensitivity and/or response times for use in a variety of fields such as optical filtering and transmission, tunable resonators and antennae, chemical and biological sensors, and actuators, for example.